Signal receiver circuit



Dec. 3, 1946. R. H.'GEORGE SIGNAL RECEIVER CIRCUIT Filed April 28, 1942QREQQQQQ E Q INVENTOR R. H. GEORGE BY ATTORNEY Batented Dec. 3, 1946star ,1.

2,411,963 SIGNAL RECEIVER CIRCUIT Roscoe H. George, West Lafayette, toRadio Corporation of America,

of Delaware Ind., assignor a corporation Application 'April 28, 1942,Serial No. 440,820

8 Claims. (01. 315 -22) The present invention relates to a system bywhich aircraft or the like may be guided efficiently. without sight ofthe significant areas toward which they are approaching, the areas fromwhich they are departing, and the areas over which they are flying.

In my prior Patent No. 2,216,707 granted October 1, 1940, a system wasdisclosed by which it was made possible for the pilot of an aircraft toguide its flight path by observing, on the viewing target of a cathoderay tube, bright spots for each marker on the airport or othersignificant area toward which, over which, or from which the airplane isflying. Provision was made, according to the patent above discussed,whereby, on the viewing screen of the cathode ray tube, the spotsrepresenting adjacent significant areas were caused to appear in correctperspective, so that the ilot would, in a sense, actually see at leastthe boundary indications of the area in question. Further provision wasmade for controlling the operation of the system so that for changes insignal strength, an efliciently operating automatic volume control wouldfunction to maintain the indications upon the viewing tube.

One form of volume control, as applied to the circuit of Patent No.2,216,707 particularly, was more specifically claimed and disclosed inPatent No. 2,289,493 issued on July 14, 1942, covering a divisionalportion of the patent hereinabove referred to.

The present invention is one tending to improve upon the blind landingsystem disclosed in the aforesaid patent and application, and to providean automatic gain or volume control for use in connection therewith,but, at the same time, provides an automatic gain control which improvesupon the arrangements hereinbefore disclosed, which held the combinedsignal of the vertical and horizontal direction finding circuits to beof substantially constant value.

The present invention has, however, as one of its primary purposes andobjects, that of providing proper observation of the resulting pattern,and at the same time, that of providing so that the ratio of thebrilliance of the resultant spots as they produce indications upon theviewing target of the cathode ray tube shall be generally inverselyproportional to the actual geographical distance of the observer fromthe significant area in question.

It has been found in the past that it is difficult to obtainextremely'great stability of operation with the types of gain controlsheretofore used when the signals change abruptly, as in the case fit'and at the same of signals transmitted with the type of blind landingsystem herein disclosed. Furthermore, with the type of automatic volumecontrol and the general receiver arrangement heretofore disclosed, thetrue illusions of perspective which are so desirable in connection witha system of blind landing or blind guiding are lost, to some extent, orat least impaired, because with the light points on the target beingrepresented at all times in the samebrilliance, irrespective of theactual location of the transmitter with regard to the plane, thisobjection has been overcome to a substantial extent by the resentdisclosure.

In its broader sense, this disclosure has as its object, that ofproviding ways and means by which the defects of prior art arrangementsare overcome. In this connection, it is possible to overcomethe defectshereinabove noted, simultaneously, by providing an automatic gaincontrol which will control the beam voltage on the oathode ray tube insuch a manner thatthe beam voltage is increased with an increase ofsignal strength. The result is that not only does the increase in thebeam voltage at the tube cause an increase in the brilliance of theresultant spot appearing upon the luminescent target of the tube becauseof the increased velocity of beam impact, but, at the same time, thedeflection sensitivity of the cathode ray tube is decreased because ofthe higher velocity of the beam resulting in a so-called stiffer beam,so that the automatic gain control thus inherently tends to provide theperspective features of the illusion. This has the effect then ofchanging the beam velocity or stiffness in such a manner that. theautomatic volume control need not act as rapidly as those provided byprior art arrangements, time provision is made so that the automaticvolume control can have a substantial voltage change produced and stillbe effective in its operation.

Other objects and advantages of the invention are those of providing asystem which Simplifies the arrangements of the prior art and at thesame time operates with a greater eificiency than did the arrangementsof the prior art. Still other objects and advantages will becomeapparent to those skilled in the art to which the invention is directedby a reading of thefollowing specification taken in connection with thesingle figure of drawings which shows a relatively simplified form ofreceiver circuit arrangement.

Referring now to the drawing, the radio frequency amplifier detectorunits I, 3, 5 and I are all schematically illustrated. In this group ofamplifiers and detectors it is intended that the units i and 3 shallconnect respectively to the left side horizontal amplifier and rectifier9, and and l to the right side horizontal amplifier and rectifier H. Theoutput from these units is adapted to energize horizontal deflectingcoils (conventionally represented at [4) connected to terminal points l3and 1-5. The horizontal deflecting coils are not shown in detail, butthe connection of-the amplifiers thereto will be apparent from what isto be indicated in connection with the vertical deflection and also fromWhat has been shown in the aforesaid Patent No. 2,216,707.

Where desired, suitable automatic volume-control features, as indicatedconventionally at H, may be incorporated with a horizontal receivingsystem. Signals to represent the as received and amplified in the radiofrequency amplifier and detector .units 5 and 1 are supplied through thetransformers 2i and 22 to be amplified in the amplifying tubes 23 and24. The output energy from these amplifying tubes is then fed by way offurther transformers 26 and 21 to two additional stages of amplificationrepresented by the tubes 23 and, 29. Operating voltages for these tubesare supplied from the terminal points and 3|, as indicated, for the D.C. potentials, and the heater elements of the various tubes areenergized from a suitable A. C. source in Well known manner (notillustrated). The output signals from the amplifiers 28 and 29 are thenfed by way of the transformers 32 and 33 to the rectifying tubes 34 and35. These tubes may be of any suitable typeknown in the art, forinstance, as the double diode, and identifiable by the type number 6H6.

The heterodynefrequency introduced on the transformers 2i and 22 intothe amplifier stages comprising the tubes 23, 24 and 28, 29 is thenfiltered out by suitable condensers 36 and 37 connected across theoutput load circuit ofthe rectifrom the tubes 34 and through thedifferel tially connected magnetic deflecting coils 38, 39 on the onehand, and 40, 4! on the other hand, and returns to ground potential atpoint 42 by way of the common output or load resistor 43. The coils 38,-39 and 40, 4| are each preferably wound in two or more parts to moreaccurately superin known manner.

Within the cathode ray tube 45 there is provided the usual electron gunstructure comprising the cathode 41, shield 46 which may serve also as acontrol electrode, an anode element 49 and-a suitable second anodeelement 50, which, together, form the cathode ray beam conventionallyindicated by the dot-dash line 5|.

At times, when signals are received in the receiver detector units 5 andI andoutput energy flows through the rectifiers 34 and 35 to produce avoltage drop across the resistor 43 caused by the combined signalcurrents, the resultant voltage drop is applied by way of a conductor 52to the control electrode 53 of an automatic gain or'automatic volumecontrol tube 54. The plate or anode element 55 high frequency voltagefrom an oscillator tube 56 vertical control of tube 54 is supplied onlywith having the tuned plate circuit comprising the inductance andcapacity elements forming the tank circuit 57 and the tuned grid circuitformed from the inductance and capacity elements forming the tankcircuit 58, and such energy is supplied to the plate or anode 55 throughthe coupling condenser 59.

In order to maintain a sufiiciently high A. C. plate voltage on the tube54, a tuned tank circuit 68, comprising the inductance element 6i andthe capacity 62, which is made resonant to the fre quency of theoscillator tube 56, is connected in series with the plate element 55 ofthe automatic Volume control tube 54. From this connection it can beappreciated that the current rectified in the plate circuit of the tube54 will be proportional, because of the control exercised by the controlelectrode 53 thereupon, to the positive potential produced across theload resistor 43 in excess of any adjustable bias that is provided byway of the conventionally indicated variable bias means 63 applied tothe cathode 64 of the au-- tomatic volume control tube 54.

As is indicated by the conductor 25, which is connected to the centertap of the secondary windings of the transformers 2| and 22, which alsoconnects to the end of the tuned circuit 60, this rectified voltage isapplied to one of the first stages of the amplifier, and, also, the samevoltage is applied by way of a second conductor 66 to the controlelectrode 61 of the high voltage tube 68. A resistance 69 is connectedbetween conductor 25 and ground to function as a grid resistor for tubes23 and 24.

The triode 68 is connected in parallel with the high resistance bleederH1 which has one terminal thereof connected to, the plate or anode 1| ofthe tube 68, and the other terminal thereof connected to ground 42 byway of the conductor 12. The bleeder resistor 10 is intended to supplythe various accelerating potentialsto the various electrodes of thecathode ray tube 45, and current to this bleeder-resistor is supplied byway of a resistor 13 which is connected at terminal point 14 to a sourceof high voltage (not shown).

Since the tube 58- is connected in parallel with the bleeder-resistor10, it is, of course, quite apparent, that the total beam voltagedeveloped within the cathode ray tube 45 may be varied over a veryconsiderable range by any variation in the current passed by the tube68, to produce a variation in the voltage drop across resistor '13.Accordingly, by a variation of the potential applied to the controlelectrode 6'! of this tube, the current flowing within the tube may bevaried within relatively wide limits, so that varying amounts of currentare by-passed from the bleeder-resistor 70.

In normal operation, the automatic gain control tube 54 is biased toapproximately a cutoif point by means of the variable bias 63. Thisbias, where desired, may be taken from the main power supply by way of asuitable potentiometer. The adjustable bias T5 for the tube 68 issuitably adjusted so that with no signal being received, the impactpoint of the cathode ray beam 5| upon the luminescent target 46 of' tube45 is just barely visible, but not of a brightness which maximum.Thus,'it is apparent that as the signal received in the amplifying anddetecting units 5 and I and the normal operating levels are obtained,the voltage from gain contro1 tube 54 is such that a' is applied to thecontrol electrode- 68 so that a decrease in the plate the automaticnegative bias 6'! of the tube less current is drawn in the shunt pathinclude.

ing thetubefiil. This decrease of current through the tube BB're's'ultsnot onlyina bright impact point on the target area '48, but also resultsin. a=decreasein sensitivity of deflection of the tube,

because it permits a higher accelerating; voltage to be applied to formthe cathode ray beam 5i, and consequently, the electronsof the beam aremoving through the tube 45 more rapidly so as to be less subject-to a'shift in location'on the target by any predetermined deflection energythan would an eIectron beam formedof less rapidly movingelectrons; .Y I

- With the arrangement as it is disclosed, the automatic gain controltube 54 is so-arranged that it can permit a considerable rise in theoutput of the receiver instrumentality, comprising the variousamplifiers hereinabove described, with any increases insign'als'trength, and yet have thisrise in the output'signal compensatedfor by the increased stiffness of the beam, that is,

the beam is moving so rapidly that/the sensitivity of the tubedeflection system-becomes less.

'It is, of course, possible'to vary, to some ex-' tent, the controlarrangement herein disclosed, by'replacing the control tube 68by-afltetrode, for instance. Transients which occur across the'c'oils'33, 39 and itl, 4| may be' rectified, where desired, andapplied, for'instance, atthe term'inal points 76, ll of the" tube 29 insuch a way as'to cut off the beam 5| developed within the tube duringthe period of readjustment when changing from a strong signal to a weakone, or the reverse.

Still other modifications may readily be made, provided suchmodifications fall fairly within the spirit and scope of what is hereinset forth and what is claimed in the claims following.

Having described the invention, what is claimed 1. Signal reproducingapparatus comprising means to receive and amplify signal energy, acathode ray tube having included therein means to develop an electronbeam and means associated therewith for deflecting the developedelectron beam under the control of applied energy, means to rectify thereceived and amplified signals, means to energize the beam deflectingmeans under the control of the said rectified signals, an automaticvolume control tube, means included within the signal reproducingapparatus for locally generating alternating current energy forenergizing said automatic volume control tube, means for applying therectified energy to the control circuit of said automatic volume controltube, and means controlled by the ouput energy of the automatic volumecontrol tube for varying the velocity of the developed cathode ray beamwhereby the intensity of the light developed thereby varies with thevariances in the intensity of the received signals.

2. The system claimed in claim 1, wherein the last named control meansincludes an electron bleeder tube.

3. Signal reproducing apparatus comprising means to receive and amplifysignal energy, a cathode ray tube having included therein means todevelop an electron beam and means associated therewith for deflectingthe developed elec tron beam under the contro1 of applied energy, meansto rectify the received and amplified signals, means toienergize thebeam deflecting means under the control 10f the said rectifiedsignala'an" automatic volume'control tube, means-included within thesignal reproducing apparatus for 10- cally generatingalternatingcurrentenergy and supplyingsaid energyto .the output circuit of. said automaticvolume control tube, means for applying the received rectified energy tothecontrol circuit of said "automatic volume control tube, an inductivemeans connected to receive the output energy fromthe'automaticvolumelcontrol tubeiand to supply said energy to theamplifier means to vary the amplification of the received signals in theamplifier, and electronic means controlled by the output energy of theautomatic, volume control tube for varying the velocity of the developedcathode ray beam.

4. Signal reproducing apparatus comprising means to receive and amplifysignal energy, an oscillation generator for generating energy at afrequency relatively high with respect to that of the signal energyreceived, a cathode ray tube having included therein means to develop anelectron beam and means associated therewith for trol of the saidrectified signals, an automatic volume control tube, means for supplyingthe 10- callyr-gen'erated high frequency energy to the output circuit ofsaid automatic'volume control tube,'and means for applying the rectifiedenergy to the control circuit of said automatic volume control tube,means responsive to the output energy' from the automatic volume controltube for varying the amplification of the received signals in theamplifier, and means controlled by the output energy of the automaticvolume control tube for varying the velocity of the developed cathoderay beam, whereby the intensity of the light developed thereby varieswith the variances in the intensity of the received signals.

5. Signal reproducing apparatus comprising means to receive and amplifysignal energy, a cathode ray tube having included therein electrodemeans to develop an electron beam and means associated therewith fordeflecting the developed electron beam under the control of appliedenergy, a bleeder resistor to control the voltage supplied to the beamforming electrodes, means to rectify the received and amplified signals,means to energize the beam deflecting means under the control of thesaid received rectified signals, an automatic volume control tube, meansfor locally generating alternating current to energize said last namedtube, means for applying the rectified energy to the input circuit ofsaid automatic volume control tube to produce an output voltageproportional to the intensity of the received signals, means responsiveto the output voltage from the automatic volume control tube for varyingthe amplitude of deflection of the developed beam and the velocity ofthe developed cathode ray beam, whereby th intensity of the lightdeveloped thereby and the raster dimensions vary with the variance inthe intensity of the received signals.

6. Signal reproducing apparatus comprising means to receive and amplifysignal energy, a cathode ray tube having included therein means i todevelop an electron beam and means associnals, meanstoenergize the beamdeflecting means.

under'the control of thesai'd amplified and rectified signals so thatthe deflectionis proportional to signal intensitman automaticxvolumecontrol tube, a. source of alternating current energy for. energizingsaid automatic volume control tube, means, for supplying the. rectifiedsignal energy. to the. control circuitof said automatic volume con! troltubev so that the output energy is, a direct current. proportional. tovthereceived signal in-.- tensity, inductive. means connected: to theoutput circuit, of the automatic volume control tube for supplying theoutput. energy therefrom .to. the amplifying means so that theamplification of the received signals in the amplifier is varied, andelectronic means also controlled bythe output energy of the automaticvolume control tube for varying the velocity of the developed cathoderay beam, whereby the intensityof the light developed thereby varieswith the variances in the intensity of the received signals and thedeflection is variable with variances in the rectified received energy.

7. A signal reproducing apparatus. comprising means to receivev andamplify independently of each other two time separated versions ofsignal energy of a. predetermined character, a cathode trol tube, meansto generate alternating current energy to energize said last named tube,means to; supply the .said; rectified and; combine signal.

energy to said last named tube, so that the. output. energy therefrom isadirect currentof an ins. tensity proportional tot-he received signalinten-, sity, means to. supply said direct, current to the amplifyingmeans, to. control the amplification level thereof and. means to.simultaneously control the intensity ,of; the cathode. ray beam deraybeam, and means associated therewith for .de-

fleeting the cathode ray beam under the control of applied energy,rectifying means for rectiiymg each of the amplified signals, meansfordififerentially applying the output of the rectifying means to. the.deflecting means for energizing said means in accordance with thedifferential output of the said two rectifying means, automatic volumecontrol means connected to develop biasing voltages proportional to thereceived signal in tensity, means for controlling the amplificationlevel of the amplifying means. in accordance with the voltage output ofthe automatic volume COD-.- trol means, and means for varying thevelocity of the cathode ray beam developed proportional to the output ofthe automatic volume control means, whereby the light initiated by theimpact of the cathode ray beam upon a target element is of an intensityproportional to the signal strength.

I ROSCOE H. GEORGE.

